The present application relates to electronic devices, and in particular, to electronic patches that can adhere to human skin or the surface of an object, including curved surfaces.
Wearable tags are a specific type of electronic patches. In general, electronic patches or stickers can be attached not only to human bodies but also to other objects such as merchandized goods such as computers, machineries, and clothes, packaging material and shipping boxes. Electronic patches can communicate with smart phones or other devices wirelessly, through NFC, Bluetooth, WiFi, or other methods.
Electronic patches can be used for tracking objects, for performing functions such as producing sound, light or vibrations, and so on. As the applications and human needs become more sophisticated and complex, there are a rapidly increasing number of tasks that electronic patches are required to perform. Because of the complex curvatures of the objects, the electronic patches are often required to be conformal to curved surfaces. In addition, the curvature of an object may vary overtime.
Wearable tags or patches can communicate with smart phones and other devices using WiFi, Bluetooth, or NFC technologies. Near Field Communication (NFC) is a wireless communication standard which enables two devices in a short range to establish a communication channel within a short period of time through radio waves in the 13.56 MHz frequency range. NFC can be a useful technology for data transfer between two devices in close proximity to one another. Because it needs the two devices to be in close proximity to one another (less than 10 cm), it is more secure than other wireless technologies like Bluetooth and Wi-Fi. Hence, it can be seen as an easy and secure tool for establishing quick two-way connections for data transfer. NFC is a two-way communication tool, one of the devices/cards can have a passive NFC tag that can reduce the cost and still behave in the same way as any other RFID tag.
Bluetooth is another wireless technology standard for exchanging data over relatively long distance in tens of meters. It uses short wavelength UHF radio waves from 2.4 to 2.485 GHz from fixed or mobile devices. Bluetooth devices have evolved to meet the increasing demand for low-power solutions that is required for wearable electronics. Benefited from relatively longer reading distance and active communication, Bluetooth module help wearable patches to continuously monitoring vital information without any human interference, which gives Bluetooth advantage over NFC solution in many applications.
Wearable tag (or patch) is an electronic patch that can be worn by a user. A wearable electronic patch is required to directly stay on user's skin and function for an extended period of time from hours to months. An electronic patch can contain a micro-electronic system and can be accessed using NFC, Bluetooth, WiFi, or other wireless technologies. An authentication wearable tag can be used as a “password” similar to a barcode. For example, it can be used to recognize a user's smart phone for authentication purpose. It can also be integrated with different sensors for other purposes such as vital signs monitoring, motion track, skin temperature measurements and ECG detection.
Despite initial development efforts, conventional wearable devices still face several drawbacks: they may not provide adequate comfort for users to wear them; they may not stay attached to user's body for the required length of time; they are usually not aesthetically appealing.
A wearable electronic patch that has sensor, computation, and communication functions usually require multiple semiconductor chips assembled on flexible printed circuits. Semiconductor chips are rigid and have three dimensions while printed circuits are made of polymer substrate that can be flexible but not deformable to respond to curvature change of the skin commonly due to muscle movements underneath. Human skin can move around with high percentage of deformation, whereas a conventional electronic patch cannot move with the same amount of strains as the skin, which is one reason for user's feeling of discomfort.
Another drawback of conventional electronic patches is that the rigid polymer substrate does not allow much breathability to the skin. The build-up of sweat and moisture can cause discomfort and irritation to the skin, especially after wearing it for an extended period of time. In addition, their rigid substrates are very difficult to conform to curved surfaces.
Moreover, conventional wearable devices are often not robust enough to sustain repeated elongations during the movements of the body that the electronic patches are attached to. Under stress, different layers in electronic patches can break or delaminate rendering the patches inoperable.
There is therefore a need for more flexible electronic patches that can stick to skin longer and are also comfortable for users to wear.